Fluid power steering gear

ABSTRACT

A fluid power steering gear is comprised of a piston installed in a cylinder and defining a pair of opposed fluid chambers therewithin, the piston being formed with rack teeth which are in mesh with the teeth of a gear sector linked to the front wheels of a motor vehicle. A steering nut is rotatably confined in this piston and is operably connected, via a plurality of endlessly recirculating balls, to a steering shaft. A pair of control valve means, respectively in communication with the aforesaid opposed fluid chambers on both sides of the piston, are also installed in the piston so as to be respectively operated by means of pins secured eccentrically to the end face of the steering nut, thereby to interrelatedly control fluid flow to and from the fluid chambers. A safety device for operation in the event of a malfunction of the fluid power steering gear is also provided.

United States Patent [191 Maekawa et a].

[54] FLUID POWER STEERING GEAR [75] Inventors: Tadashi Maekawa; AkiraSuzuki; Shigenori Haramura, all of Kariya, Japan [73 Assignee: AisinSeiki Kabushiki Kaisha, Aichiken, Japan 22 Filed: Feb. 12,1971

211 Appl.No.: 114,864

[52] US. Cl. ..91/380, 91/422, 91/465, 92/ 1 16 [51] Int. Cl ..F15b 9/0[58] Field of Search ..91/422, 431, 465, 370, 380, 91/371, 372, 373,374, 376, 378; 180/792 51 Mar. 27, 1973 Primary Examiner-Paul E.Maslousky Attorrtey-J-lolman & Stern ABSTRACT A fluid power steeringgear is comprised of a piston installed in a cylinder and defining apair of opposed fluid Chambers therewithin, the piston being formed withrack teeth which are in mesh with the teeth of a gear sector linked tothe front wheels of a motor vehicle. A steering nut is rotatablyconfined in this piston and is operably connected, via a plurality ofendlessly recirculating balls, to a steering, shaft. A pair of controlvalve means, respectively in communication with the aforesaid opposedfluid chambers on both sides of the piston, are also installed in thepiston so as to be respectively operated by means of pins securedeccentrically to the end face of the steering nut, thereby tointerrelatedly control fluid flow to and from the fluid chambers. Asafety device for operation in the event of a malfunction of the fluidpower steering gear is also provided. 1 v

8 Claims, 4 Drawing Figures PAIENTEBHA N 3,722,369

SHEET 2 BF 2 FIG. 2

FIG.3

BACKGROUND OF THE INVENTION This invention relates generally to fluidpower steering, and in particular to a new and improved integral" fluidpower steering gear for particular use in motor vehicles, wherein a pairof control valve means are accommodated in a piston within a cylinderhousing the steering gear proper.

There have been proposed various types of such integral steering gear,e.g., those having their power mechanism built into the same housing asthe steering gear proper. In spite of their many manifested advantages,those conventionally available integral steering gears have had aserious disadvantage arising from their bulky size when they are to beinstalled in a limited space available therefor within present day motorvehicles which are packed with a growing number of components foraccessories. Todays demand for smaller sized integral steering gears hasnot been fully fulfilled by the prior art, as far as we are aware,without the slightest sacrifice in operating efficiency or manufacturingcosts.

SUMMARY OF THE INVENTION It is accordingly a principal object of thepresent invention to provide an improved integral fluidpower steering.gear which is greatlyreduced in size and which operates with highefficiency.

Another objectofthe invention lSlIOiPI'OVlClC a fluid power steeringgearin which a pair of control valve means are accommodated in a pistonwithin a cylinder housing the steering gear proper, thus resulting ingreat reduction inthe overall length of the cylinder.

Still another object of the invention is to provide a fluid powersteering gear in which :the inner sleeve members of a pair of controlvalves accommodated in a piston are operated directly by the rotation ofa steering nut also confined in the piston, the inner sleeve members sooperated correspondingly controlling fluid flow to and fromfluidchambers on both sides of the piston within the cylinder, sothat theforce applied at the motor vehicle steering wheel by an operator isfaithfully responded to by its front wheels.

A further object of the invention is to provide a fluid power steeringgear equipped with a simple but positive safety device whereby the motorvehicle can be steered safely even in the event of damage or some othertrou- FIG. 3 is a fragmentary sectional view taken along the lineIII-III in FIG. 2, the view looking in the direction of the arrows; and

FIG. 4 is a fragmentary sectional view taken along the line IV-IV inFIG. I, the. view looking in the direction of the arrows.

' DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings,and first of all to FIG. 1 in particular, wherein is shown a preferredform of the fluid power steering gear in accordance with the presentinvention, the reference numeral 1 generally designates a cylinderhousing the fluid power steering gear propenln a circular bore 2 of thiscylinder 1, there is slidably installed a piston 3 defining a left handfluid chamber 4 and a right hand fluid chamber 5. A gear sector 6,positioned in a space 7 in communication with the right hand fluidchamber 5, is connected to the front wheels (not shown)of the motorvehicle through a pitman arm and a steering linkage system on one handand, on the other, is in mesh with rack teeth formed on part of theaforesaid piston 3. A steering shaft 8 is'connected to a steering wheel(not shown) of the motor vehicle and is itself installed lengthwise inthe cylinder 1 so as to extend through the piston 3. Bearings 9 and 10support this steering shaft 8 so as to permit its s smooth rotation andyet to prevent its axial movement.

balls 15 interposed between a helical groove 13 on the inner surface ofthe steering nut .11 and a corresponding helical groove 14 on theperiphery of the left hand me that may be caused in the hydrauliccircuit of the steering gear.

With these objects in view and the other objects hereinafter setforth,the present invention will now be described in greater detail in termsof a preferred embodiment thereof illustrated in the accompanyingdrawings, throughout which like referencenumerals indicate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a longitudinal sectional view of a fluid power steering gearin accordance with the present invention;

FIG. 2 is a cross sectional view of the fluid power steering gear ofFIG. 1, taken along line II-II therein, the view looking in thedirection of the arrows;

side of the steering shaft8. This steering nut 11 is supported bybearings 17 and 18 so as to be rotatable but to' be prevented from axialmovement, and its rotational resistance is made regulatable by means ofa lock screw 16 screwed into the lefthand end of the piston 3.

As illustrated in FIG. 1 and,.in greater detail, in FIG. 4, a keyway 19is cut axially on the lower end of the steering nut 1 1, with ake y 20being securely received by this keyway 19. This key 20protrud-es into akeyway 21 cut correspondingly atthe bottom of a bored (12) interior ofthe piston 3,' with substantially equal spacings between the key 20 andshoulders'22 and 23 of the keyway 2 1. This is to permit vehiclesteering solely by the force applied manually at the steering wheel (notshown)in the event of some trouble caused especially in the hydrauliccircuit of the fluid power steering gear, as still to be described ingreater detail.

As illustrated specifically in FIGS. 2 and 3, the piston 3 is providedwith a pair of bores 24 and 25 which are disposed symmetrically withrespect to the axis of this piston 3 and in a plane at right anglesthereto. Within these bores 24 and 25 there are fixedly confined outervalve sleeve members 26 and 27, respectively, in which are slidablyreceived inner valve'sleeve members 28 and 29, respectively. Formed atthe central portions of these inner sleeve members 28 and 29 areelongated holes 30 and 31, respectively, with which are respectivelyengaged pins 33 and 33' secured at the other end to a pair of bores 32and 32 (the bore 32- being not shown in the drawings) formedeccentrically at the end of the steering nut 11. Hence, the inner sleevemembers 28 and 29 are made by the rotation of this steering nut 11 toslide up and down in the opposite directions and in parallel with eachother in a plane at right angles to the steering shaft 8.

Proceeding now to the description ofa hydraulic circuit of this fluidpower steering gear, the reference numeral 34 in FIG. 1 indicates asource of pressure fluid (e.g., a pump) located outside of the cylinder1 enclosing the fluid power steering gear proper. This source 34 ofpressure fluid is communicated via a passage 35 with a connector 36 tothe power steering gear proper, with the connector 36 being incommunication with a groove 37 extending axially on the periphery of thepiston 3 over a length substantially equal to the stroke of this piston3. Further, as illustrated in FIG. 2, the connector 36 is communicatedvia passages 38 and 39, bifurcated from the axial groove 37, with ports40 and 41 running in the radial direction of the outer sleeve members 26and 27, respectively. A seal member 42 is positioned in the axial groove37 on the periphery of the piston 3 and is kept in place by means of aholding member 43. Aided by a ring 44, this seal member 42 adequatelyprevents the leakage of the fluid being fed under pressure into the lefthand fluid chamber 4 and the right hand fluid chamber 5.

Between the outer sleeve member 26 and the inner sleeve member 28together with its lands 28a and 28b, there are provided annular chambers45, 46, 47 and 48. Similarly, between the other outer sleeve member 27and the other inner sleeve member 29 together with its lands 29a and29b, there are provided annular chambers 49, 50, 51 and 52. Of all theseannular chambers, the chambers 45 and 49 are respectively incommunication with the aforesaid ports 40 and 41 running in the radialdirection of the outer sleeve members 26 and 27. The chambers 47 and 51are in communication with a reservoir 63 via passages 53 and 53' (thepassage 53' being not shown in the drawings) extending radially throughthe outer sleeve members 26 and 27, a passage 54 extending axiallythrough the piston 3, a passage 55 extending obliquely through thepiston 3, an annular passage 56 between the piston 3 and the steeringshaft 8, a passage 57 extending diametrically through the steering shaft8, a passage 58 extending axially through the steering shaft 8, apassage 59 extending diametrically through steering shaft 8, a passage60 provided to the cylinder 1 housing the steering gear proper,connector 61 and a passage 62 outside of the cylinder 1, as illustratedin FIGS. 1, 2 and 3.

In order to make watertight all of the aforementioned passages as wellas the left hand fluid chamber 4 and the right hand fluid chamber 5,there are provided seal members wherever necessary. Further, the annularchamber50 is in communication with the-right hand fluid chamber via aport 64 extending diametrically through the inner sleeve member 29, apassage 65 extending axially through the same inner sleeve member 29 anda hole 66 formed in the piston 3 and opened to the space 7, asillustrated in FIG. 2 in particular. The annular chamber 46 is incommunication with the left hand fluid chamber4 via a port 67 extendingradially through the outer sleeve member 26, a slot 68 formed on theperipheryof the same, a hole 69 open to the bore 12 of the piston 3, agroove 71, and finally through an annular passage 70 between thesteering nut 11 and the piston 3, as best illustrated in FIGS. 1 and 3.

Being of the so-called open center type, the annular chambers 45 and 46,the annular chambers 46 and 47, the annular chambers 49 and 50, and theannular chambers 50 and 51 are respectively in communication with eachother when the inner sleeve members 28 and 29 are kept in their neutralor centered position by means of spring members 72 and 73 accommodatedin their respective annular chambers 48 and 52.

In the above described construction of the preferred form of the fluidpower steering gear in accordance with the present invention, when themotor vehicle is running straight ahead, the open center type innersleeve members 28 and 29 intercommunicate all the fluid paths associatedtherewith. Accordingly, the fluid fed under pressure from the source 34is supplied via the passage 35, the connector 36, the axial groove 37 onthe periphery of the piston 3 and the passages 38 and 39 bifurcatedtherefrom, to the ports 40 and 41 extending in the radial direction ofthe outer sleeve members 26 and 27, respectively. Further from theseradial ports 40 and 41, the fluid is fed to the left hand fluid chamber4 and the right hand fluid chamber 5 via the annular chambers 45 and 49,the spaces opened slightly by the lands 28a and 29a of the inner sleevemembers 28. and 29', and the annular chambers I 46 and 50, respectively.In this instance, however, the pressures thus produced in the left handfluid chamber 4 and the right hand fluid chamber 5 are equalized, sothat no thrust is caused to thepiston 3. Consequently, the fluid in theannular chambers 46 and 50 is fed through the spaces opened slightly bythe lands 28b and 29b of the inner sleeve members 28 and 29 to theannular chambers 47 and 51, respectively, and thence to the reservoir 63through the discharge path mentioned already.

It will now be supposed that the steering shaft 8 is rotated in thedirection of the arrow A in FIG. 1 by an operator at the motor vehiclesteering wheel. Then the gear sector 6, connected to the front wheels ofthe motor vehicle through a pitman arm and a steering linkage mechanism,is prevented from rotating because of the road surface resistanceexperienced by the front wheels, thereby inhibiting the movement of thepiston 3. Hence the steering nut 11 rotates together with the steeringshaft 8. Since the pins 33 and 33' secured eccentrically to the end ofthe steering nut 11 are in-engagement with the elongated holes 30 and 31formed at the central portions of the inner sleeve members 28 and 29,respectively, these inner sleeve members 28 and 29 are axially displacedagainst the force of the springs 73 and 74 due to the rotation of thesteering nut 1 1.

More specifically, with reference to FIG. 2, the inner sleeve member 28moves upward while the other inner sleeve member 29 moves downward, asindicated by the arrows in the drawing, so that their lands 28a and 29bopen the annular chambers while their lands 28b and 29a close theannular chambers associated respectively therewith. The fluid being fedunder pressure as described above thus flows into the annular chambers45 and 49 via the radial ports 40 and 41 of the outer sleeve members 26and 27, respectively, and thence into the annular chamber 46 alone pastthe land 28a of the inner sleeve member 28 because the annular chamber50 below the aforesaid annular chamber 49 is closed by the land 29a ofthe inner sleeve member 29. Further from this annular chamber 46, thefluid is fed under pressure into the'left hand fluid chamber 4 via theradial port 67 of the outer sleeve member 26, the

slot 68 formed on the periphery of the same, the hole 69 open to thebore 12 of the piston 3, the groove 71 and the annular passage 70between the steering nut 1 1 and the piston 3, and thence to thechamber, as illustrated in FIG. 3. Hence the piston 3 is thrusted in theright hand direction in FIG. 1.

succeedingly, the fluid that has been present in the right hand fluidchamber Sis forced through the hole 66 open to the space 7 incommunication with that right hand fluid chamber 5, the passage 65extending in the axial direction of the inner sleeve member 29, and theport 64 extending diametrically through the same inner sleeve member 29,into the annular chamber 50, and thence into the annular chamber 51therebelow via the space opened by the land 29b of the downwardlydisplaced inner sleeve member 29. The fluid in the right hand fluidchamber 5 is thus fed back to the reservoir 63 of FIG. 1 through theensuing discharge path mentioned already.

The piston 3 thrusted in the right hand direction in FIG. 1 as describedabove causes the gear sector 6 to turn clockwise in the drawing, so thatthe motor vehicle is steered as its front wheels, connected with thisgear sector 6 through the pitman arm, etc., are turned cor-,

respondingly. The inner sleeve members 28 and 29 are succeedinglyreturned to their neutral or centered position upon cessation of theapplication of turning effort at the steering wheel. i

A turn of the motor vehicle in the other direction is effected throughthe reversal of the foregoing action, with the steering shaft 8 thenbeing rotated in the direction of the arrow B in FIG. 1.

In the event of a damage or other trouble caused in the hydrauliccircuit of the fluid power steering gear, whereby the motor vehicle mustbe steered solely by the manually applied force at the steering wheel,the key 20 secured to the steering nut 11 comes into contact with eitherone of the shoulders 22 and 23 of the keyway 21 of the piston3 uponrotation of the steering shaft 8. The piston 3 thus solidly engaged withthe steering nut 11 is made to move either rightward or leftward in FIG.1 through the recirculating balls 15, thereby turning the gear sector 6either clockwise or counterclockwise in the drawing and hence causingthe motor vehicle to make a desired turn.

Although a preferred form of the fluid power steering gear of thepresent invention has been shown and described in the foregoing, it isunderstood that the invention itself is not to be restricted thereby butto be interpreted broadly and in a manner consistent with the spirit andscope of the invention.

We claim:

1. A fluid power steering gear comprising, in combination, a cylinder, ahydraulic circuit through which fluid is made to flow by means of apressure source located outside of said cylinder, a piston installed insaid cylinder and defining a pair of opposed chambers therewithin, saidpiston being operably engaged with an oscillatable member connected to aload, a rotatable member confined in said piston and operably connectedto a shaft extending into said cylinder, said shaft being actuablebymanually applied force, and a pair of control valve means alsoinstalled in said piston andv having inner sleeve members received bystationary outer sleeve members so as to be displaced in oppositedirections therein by actuating means operating through said rotatablemember to actuate said control valve means when said shaft rotates forrespectively and interrelatedly controlling fluid flow to and from saidchambers in said hydraulic circuit.

2. A fluid power steering gear as claimed in claim 1 in which saidactuating means comprises pins secured eccentrially to the end face ofsaid rotatable member.

3. A fluid power steering gear as claimed in claim 2, in which therotational resistance of said rotatable member is regulatable by meansof a threaded member screwed into said piston.

4. A fluid power steering gear comprising, in combination, a cylinderhaving an inlet and an outlet for fluid fed through a hydraulic circuitby means of a pressure source located outside of said cylinder, a pistoninstalled in said cylinder and defining a pair of opposed chamberstherewithin, said piston having rack teeth on part of the body thereofwhich arein mesh with teeth formed on an oscillatable member connectedto a load, a rotatable member confined in said piston and operablyconnectedvia a plurality of endlessly recirculating balls to a shaftextending into said cylinder, said shaft being actuable by manuallyapplied force, and a pair of control valve means also installed in saidpiston and arranged in parallel with each other in a plane extendingperpendicularly with respect to the axis of said shaft, said controlvalve means having inner sleeve members received by stationary outersleeve members so as to be axially displaced in opposite directionstherein by means of pins secured ecceritrically to the end of saidrotatable member, whereby fluid flow to and from said chambers in saidhydraulic circuit is interrelatedly controlled.

5. In a fluid power steering gear, a hydraulic circuit comprising, incombination, a source of pressure fluid, a connector from said source ofpressure fluid into a cylinder in which is housed said fluid powersteering gear, said connector being in open communication with an axialgroove formed on the periphery of a piston installed in said cylinder,said axial groove extending over a length substantially equal to thestroke of said piston, and a first and a second control valvemeansinstalled transversely in said piston and having radial portsrespectively in open communication with said axial groove via passagesbifurcated from said axial groove, each of said first and said secondcontrol valve means having a stationary outer sleeve member in which isslidably installed an inner sleeve member having a first and a secondland, said inner sleeve members of said first and said secondcontrolvalve means being normally kept in a centered position thereby to permitfluid flow throughout said hydraulic circuit, each of said first andsaid second control valve means further comprising first, second, thirdand fourth annular chambers between said outer sleeve member and saidinner sleeve member, said first annular chambers of said first and saidsecond control valve means being respectively in opencommunication withsaid radial ports, said second annular chambers being respectivelynormally in communication with said first annular chambers on one handand being respectively in open communication with a pair of chambersdefined by said piston within said cylinder on the other hand, one ofsaid second annular chambers being closed from the corresponding one ofsaid first annular chambers by the corresponding one of said first landsof said inner sleeve members upon simultaneous operation of said innersleeve members, and said third annular chambers being respectivelynormally in communication with said second annular chambers on one handand being in open communication with a reservoir located outside of saidcylinder via said connector on the other hand, one of said third annularchambers being closed from the corresponding one of said second annularchambers by the corresponding one of said second lands of said innersleeve members upon simultaneous operation of said inner sleeve members.

6. A hydraulic circuit as claimed in claim 5, in which said inner sleevemembers of said first and said second control valve means are normallymaintained at their respective centered position by means of elasticmembers accommodated respectively in said fourth annular chambers ofsaid first and second control valve means.

7. A fluid power steering gear as claimed in claim 1 in which a safetydevice comprising a key projecting from said rotatable member andreceived with allowance in a keyway cut axial on an internal surface ofsaid piston.

8. A hydraulic circuit as claimed in claim 5 in which there are providedcommunication means between said reservoir and said third annularchamber, said commu nication means comprising, essentially, a passage 56

1. A fluid power steering gear comprising, in combination, a cylinder, ahydraulic circuit through which fluid is made to flow by means of apressure source located outside of said cylinder, a piston installed insaid cylinder and defining a pair of opposed chambers therewithin, saidpiston being operably engaged with an oscillatable member connected to aload, a rotatable member confined in said piston and operably connectedto a shaft extending into said cylinder, said shaft being actuable bymanually applied force, and a pair of control valve means also installedin said piston and having inner sleeve members received by stationaryouter sleeve members so as to be displaced in opposite directionstherein by actuating means operating through said rotatable member toactuate said control valve means when said shaft rotates forrespectively and interrelatedly controlling fluid flow to and from saidchambers in said hydraulic circuit.
 2. A fluid power steering gear asclaimed in claim 1 in which said actuating means comprises pins securedeccentrially to the end face of said rotatable member.
 3. A fluid powersteering gear as claimed in claim 2, in which the rotational resistanceof said rotatable member is regulatable by means of a threaded memberscrewed into said piston.
 4. A fluid power steering gear comprising, incombination, a cylinder having an inlet and an outlet for fluid fedthrough a hydraulic circuit by means of a pressure source locatedoutside of said cylinder, a piston installed in said cylinder anddefining a pair of opposed chambers therewithin, said piston having rackteeth on part of the body thereof which are in mesh with teeth formed onan oscillatable member connected to a load, a rotatable member confinedin said piston and operably connected via a plurality of endlesslyrecirculating balls to a shaft extending into said cylinder, said shaftbeing actuable by manually applied force, and a pair of control valvemeans also installed in said piston and arranged in parallel with eachother in a plane extending perpendicularly with respect to the axis ofsaid shaft, said control valve means having inner sleeve membersreceived by stationary outer sleeve members so as to bE axiallydisplaced in opposite directions therein by means of pins securedeccentrically to the end of said rotatable member, whereby fluid flow toand from said chambers in said hydraulic circuit is interrelatedlycontrolled.
 5. In a fluid power steering gear, a hydraulic circuitcomprising, in combination, a source of pressure fluid, a connector fromsaid source of pressure fluid into a cylinder in which is housed saidfluid power steering gear, said connector being in open communicationwith an axial groove formed on the periphery of a piston installed insaid cylinder, said axial groove extending over a length substantiallyequal to the stroke of said piston, and a first and a second controlvalve means installed transversely in said piston and having radialports respectively in open communication with said axial groove viapassages bifurcated from said axial groove, each of said first and saidsecond control valve means having a stationary outer sleeve member inwhich is slidably installed an inner sleeve member having a first and asecond land, said inner sleeve members of said first and said secondcontrol valve means being normally kept in a centered position therebyto permit fluid flow throughout said hydraulic circuit, each of saidfirst and said second control valve means further comprising first,second, third and fourth annular chambers between said outer sleevemember and said inner sleeve member, said first annular chambers of saidfirst and said second control valve means being respectively in opencommunication with said radial ports, said second annular chambers beingrespectively normally in communication with said first annular chamberson one hand and being respectively in open communication with a pair ofchambers defined by said piston within said cylinder on the other hand,one of said second annular chambers being closed from the correspondingone of said first annular chambers by the corresponding one of saidfirst lands of said inner sleeve members upon simultaneous operation ofsaid inner sleeve members, and said third annular chambers beingrespectively normally in communication with said second annular chamberson one hand and being in open communication with a reservoir locatedoutside of said cylinder via said connector on the other hand, one ofsaid third annular chambers being closed from the corresponding one ofsaid second annular chambers by the corresponding one of said secondlands of said inner sleeve members upon simultaneous operation of saidinner sleeve members.
 6. A hydraulic circuit as claimed in claim 5, inwhich said inner sleeve members of said first and said second controlvalve means are normally maintained at their respective centeredposition by means of elastic members accommodated respectively in saidfourth annular chambers of said first and second control valve means. 7.A fluid power steering gear as claimed in claim 1 in which a safetydevice comprising a key projecting from said rotatable member andreceived with allowance in a keyway cut axial on an internal surface ofsaid piston.
 8. A hydraulic circuit as claimed in claim 5 in which thereare provided communication means between said reservoir and said thirdannular chamber, said communication means comprising, essentially, apassage 56 formed between the piston 3 and the steering shaft 8 andthree passages 57, 58, and 59 formed within the steering shaft.